The utilization of chemical shift and spin-lattice (T1) relaxation time data for the discrimination of isomeric indenoisoxazoles

Treatment of 2-pivaloyl-1,3-indandione with hydroxylamine leads to the formation of a pair of isomeric indenoisoxazoles, the product formed dependent upon the cyclization conditions. Under acidic conditions, 8-t-butylindeno[1,2-c]isoxazol-7-one ( 5 ) is formed while under neutral or basic conditions, an oxime, 2 , is generated which may then be cyclized under acidic conditions to give 3-t-butylindeno[1,2-c]isoxazol-4-one ( 4 ). Although these isomeric indenoisoxazoles may be discriminated by chemical means, we were interested in developing an unequivocal method for distinguishing these and potentially other isomeric pairs by spectroscopic means. A ¹³C-nmr based method for the discrimination of these isomers which is based on the utilization of chemical shift arguments and spin-lattice relaxation data is thus presented.     

Chemistry of the phenoxathiins and isosterically related heterocycles. XXV . Synthesis of 1,6-diazathianthrene from 3-mercaptopyridin-2(1H)-thione via a novel dehydrothiolation reaction in the presence of triethylamine

The generation of the dianion of 3-mercaptopyridin-2(1H)-thione with triethylamine in N,N-dimethylform-amide followed by reaction in the presence of 2-chloronitrobenzene fails to give 1-azathianthrene which is formed in good yield when sodium hydride was employed as the base. The principle product isolated from the reaction was instead 1,6-diazathianthrene. Mechanistic considerations are discussed.     

Torsional fatigue tests of anodized aluminum rods

Fatigue tests in reversed torsion were run on 2024-T351 aluminum-alloy specimens in (1) uncoated state and (2) anodized with 0.3 and 0.05-mil (0.0076- and 0.0013-mm) coatings. Tests on both groups were run at low (20–25 percent), medium (55–60 percent), and high (86–91 percent) relative humidity. One lot of uncoated specimens was tested that had been polished after machining, and one lot of anodized specimens was tested that had been polished before coating. Tests on uncoated and on anodized specimens were run at stress levels of approximately 13,000, 17,000 and 20,000 psi (89.62, 117.2 and 137.9 MPa, respectively). Results of tests on both coated and uncoated specimens showed longer fatigue life at low humidity than at high humidity. Little difference was found between tests at medium and at high humidity. No difference was found between polished and unpolished specimens. With coated specimens, the thickness of coating showed no effect on fatigue life. Comparing the results on coated and uncoated specimens at low humidity, coated specimens had a longer fatigue life. However, at high humidity, there was no significant difference.     

Chemistry of the phenoxathiins and isosterically related heterocycles. XIX.. The crystal and molecular structure of 1-N,N-dimethylamino-2,3-diazaphenoxathiin: An interesting product isolated from the reaction of o-mercaptophenol with 3,4,5-trichloropyridazine in N,N-dimethylformamide

The isolation of 1-N,N-dimethylamino-2,3-diazaphenoxathiin and its molecular structure as determined by X-ray crystallography are described. The existence of a potential non-bonded interaction between the lone pair of electrons of the dimethylamino group nitrogen and sulfur atom are also discussed.     

Bayesian Variable Selection on Model Spaces Constrained by Heredity Conditions

This article investigates Bayesian variable selection when there is a hierarchical dependence structure on the inclusion of predictors in the model. In particular, we study the type of dependence found in polynomial response surfaces of orders two and higher, whose model spaces are required to satisfy weak or strong heredity conditions. These conditions restrict the inclusion of higher-order terms depending upon the inclusion of lower-order parent terms. We develop classes of priors on the model space, investigate their theoretical and finite sample properties, and provide a Metropolis–Hastings algorithm for searching the space of models. The tools proposed allow fast and thorough exploration of model spaces that account for hierarchical polynomial structure in the predictors and provide control of the inclusion of false positives in high posterior probability models.     

CHILDREN INVENTING SIGNS FOR MENTAL NUMBER STRATEGIES

The research study described here was conducted with a small group of 5- and 6-year-old children in a 35-pupil rural school in the Langdale Valley (Lake District, UK) over a period of 14 weeks. It considers the theoretical implications of children inventing their own signs for their counting actions instead of using the culturally inherited signs of conventional arithmetic. It also raises questions concerning ‘transformational addition’ in which ordinals (‘position numbers’) are distinguished from cardinals (‘size numbers’), and suggests that the invented signs may have a consistency and validity comparable with the signs of conventional arithmetic.     

Imaging of lipids in rat heart by MALDI-MS with silver nanoparticles

Lipids are a major component of heart tissue and perform several important functions such as energy storage, signaling, and as building blocks of biological membranes. The heart lipidome is quite diverse consisting of glycerophospholipids such as phosphatidylcholines (PCs), phosphatidylethanolamines (PEs), phosphatidylinositols (PIs), phosphatidylglycerols (PGs), cardiolipins (CLs), and glycerolipids, mainly triacylglycerols (TAGs). In this study, mass spectrometry imaging (MSI) enabled by matrix implantation of ionized silver nanoparticles (AgNP) was used to map several classes of lipids in heart tissue. The use of AgNP matrix implantation was motivated by our previous work showing that implantation doses of only 10¹⁴/cm² of 2 nm gold nanoparticulates into the first 10 nm of the near surface of the tissue enabled detection of most brain lipids (including neutral lipid species such as cerebrosides) more efficiently than traditional organic MALDI matrices. Herein, a similar implantation of 500 eV AgNP^? across the entire heart tissue section results in a quick, reproducible, solvent-free, uniform matrix concentration of 6 nm AgNP residing near the tissue surface. MALDI-MSI analysis of either positive or negative ions produce high-quality images of several heart lipid species. In negative ion mode, 24 lipid species [16 PEs, 4 PIs, 1 PG, 1 CL, 2 sphingomyelins (SMs)] were imaged. Positive ion images were also obtained from 29 lipid species (10 PCs, 5 PEs, 5 SMs, 9 TAGs) with the TAG species being heavily concentrated in vascular regions of the heart.     

Gas‐Phase Structure Determination of Dihydroxycarbene,One of the Smallest Stable Singlet Carbenes

Carbenes are reactive molecules of the form R¹ C̈ R² that play a role in topics ranging from organic synthesis to gas‐phase oxidation chemistry. We report the first experimental structure determination of dihydroxycarbene (HO C̈ OH), one of the smallest stable singlet carbenes, using a combination of microwave rotational spectroscopy and high‐level coupled‐cluster calculations. The semi‐experimental equilibrium structure derived from five isotopic variants of HO C̈ OH contains two very short CO single bonds (ca. 1.32 Å). Detection of HO C̈ OH in the gas phase firmly establishes that it is stable to isomerization, yet it has been underrepresented in discussions of the CH₂O₂ chemical system and its atmospherically relevant isomers: formic acid and the Criegee intermediate CH₂OO.